722 BEPORT— 1887. 



observed were in some cases limestone and not very hard grits; in others vaiioos 

 crystalline rocks, such as granite, gneiss, or mica-schist. Hence, as the majority of 

 the pehbles in the Bunter are of harder material, and are generally better rounded 

 than those which the author observed, he concludes that it is impossible to suppose 

 them mainly derived from any tract of land which, in Triassic times, can have existed 

 in either Central or Eastern England, for thej' must have been formed by rivers 

 no less important, with courses either longer or steeper than those of Central 

 Europe. Thus these observations are very favourable to the view which ascribes to 

 them a Scotch origin, where alone rocks exactly like them are known to occur. 



5. On the Present State of the Channel Tunnel, and on the Boring at 

 Shakespeare Cliff, near Dover. By Professor W. Boyd Dawkins, F.R.8. 



The present condition of the experimental heading of the Channel Tunnel 

 Company is now, after the lapse of five years, a most important fact bearing on the 

 feasibility of a Channel tunnel at all. 



A careful examination of the heading on July 2.3, 1887, proves that the con- 

 clusions which were arrived at when the enterprise was begun, as to the ease with 

 which a tunnel can be constructed, the security from inroads of the sea resulting 

 from its being made in the grey chalk, and the small cost at which it can be made 

 and maintained, have been fully justified by the present condition of the works. 



The heading, 7 feet in diameter and IJ miles in length, and for upwards of a 

 mile actually beneath the sea-bottom, is practically free from water. In driving it 

 the total quantity of water met with amounted only to 3g gallons per minute. This 

 small amount has now diminished to the odd one-third of a gallon per minute, 

 almost all of which is derived from a spring in the broken materials in the 

 shaft, occurring 30 feet from the surface. The fact that the heading not only 

 remains dry after standing for five years, but is drier now than when it was driven, 

 shows that no danger is to be anticipated from the inroad of the sea into the tunnel 

 beneath the bottom of the Straits of Dover, or from the influx of water from the 

 land. 



Nor has the heading shown any signs of movement, although it is unlined, and 

 has been exposed to atmospheric agencies for five years. The chalk has not swelled 

 or changed its form ; it retains the tool-marks of the boring machine, as clearly and 

 sharply defined as on the day when they were made. It stands perfectly, and has 

 become harder, as it has lost the water in its capillary pores. 



The dip of the strata lends itself with singular facility to the gradients which 

 are best adapted to the working of the traflSc, and the defence of the tunnel by 

 flooding. 



After taking all these facts into consideration, it is clear that the original 

 estimate for the English half of the tunnel of 1,527,000/. is amply confirmed by 

 the experience obtained. The dryness and stability of the heading prove further 

 that the cost of the maintenance of the tunnel will be exceptionally low. 



The geological evidence is conclusive that the valuable coalfields of South 

 Wales and of Somerset are connected witli the equally valuable coalfields of North 

 France and Belgium, some 1,200 square miles in extent, by a series of isolated fields 

 or basins concealed by the newer rocks. The coal-measures in Northern France 

 pass westwards in the direction of Calais, and plunge under the newer rocks near 

 Conde, from which point to Therouanne they extend and are worked under two 

 departments, their discovery being due to boriugrs carried out at the expense of the 

 French Government. The last-named place, some 30 miles to the east of Calais, is 

 the farthest point to the west where they liave been worked. At Calais, however, 

 they have been proved at a depth of 1,092 feet below Ordnance datum. From this 

 point westward they have not been struck initil we reach Somersetshire. 



The borings for water, however, made in the London area show that the water- 

 worn primary rocks which come to the surface in the West of England and in 

 North France and Belgium occur under London at a distance of not more than 

 1,200 feet from the surface, and that these are highly inclined as in those regions. 



